Compressor

ABSTRACT

A compressor ( 10, 100 ), comprising a compressor housing ( 15 ), a drive mechanism ( 12 ), and a compressing unit ( 14 ) having one or several compression levels ( 14 - 1, 14 - 2 ) for compressing a cooling agent, wherein the compressor ( 10, 110 ) is further provided with one or several cooling agent feeder units ( 20, 36 ) for feeding cooling agents to the compressing unit ( 14 ) and with one or several cooling agent discharge units ( 24, 38 ) for discharging cooling agents from the compressing unit ( 14 ). At least one segment of the one cooling agent feeder unit or at least one segment of at least one, in particular each one of the several cooling agent feeder units ( 20, 36 ), is arranged thermally separated from the one cooling agent discharge unit or at least one, in particular each one of the several cooling agent discharge units ( 24, 38 ).

The invention relates to a compressor as per the preamble of patent claim 1, and to a refrigeration system as per claim 15.

Compressors such as are known from the preamble of patent claim 1 have a drive device and a compression device. The drive device is for example often an electric motor. The compression device is of single-stage or multi-stage design, which means that, for example, the compressor compresses refrigerant from a low pressure (intake pressure) to an intermediate pressure in a first stage, wherein the refrigerant at intermediate pressure is then fed to a second stage, in which it is compressed to a high pressure (end pressure).

The efficiency of two-stage compressors is however often not optimal. This fact takes on increasing significance if it is intended to use “new, natural” refrigerants, that is to say for example R744 (CO₂), which place particular demands on the conditions of the compression process.

Taking the prior art discussed above as a starting point, it is accordingly an object of the present invention to specify a compressor which has increased efficiency in relation to the compressors according to the prior art and which is suitable in terms of energy for operation with all common refrigerants. It is also an object of the present invention to specify a correspondingly configured refrigeration system.

Said object is achieved according to the invention by means of a compressor as per patent claim 1, and by means of a refrigeration system as per claim 15.

According to the invention, a compressor has a compressor housing, a drive device and a compression device with one or more compression stages for compressing a refrigerant. The compressor furthermore has at least one refrigerant feed device for feeding refrigerant to the compression device and at least one refrigerant discharge device for discharging refrigerant from the compression device, wherein at least one section of the refrigerant feed device is arranged so as to be thermally separate from the refrigerant discharge device or the refrigerant discharge devices.

By means of such a construction, it is achieved that there is no excessive heat transfer from compressed refrigerant to be discharged, which has been heated as a result of a prior compression process, to the refrigerant flowing through a section of the feed device. In other words, by means of such a construction, the heat transfer from a compressed refrigerant that has been heated as a result of the compression process to a non-compressed refrigerant is substantially prevented. The greater the effectiveness with which the respective sections of the refrigerant feed device(s) are thermally separate or decoupled from those of the corresponding refrigerant discharge device(s), the lower the heat transfer. It is ideally provided that not only sections but in each case the devices in their entirety are completely thermally separate from one another, that is to say the devices are completely thermally separate from one another over their entire extent, which leads to a minimal transfer of heat. It is however pointed out at this juncture that individual contact points or contact areas (heat transfer areas) between the respective devices are practically unavoidable from a construction aspect, but the amounts of heat transmitted via these contact points or contact areas are relatively low and thus tolerable. With regard to the size of the contact areas (heat transfer areas), it is possible in accordance with the specific situation to select the respectively most economical concept which allows for both production costs and also operating costs. It is also mentioned at this juncture that it is for example also possible to achieve a minimal exchange of heat with the surroundings of the refrigerant discharge device(s) by designing the surfaces of the refrigerant discharge device(s) to be as small as possible.

In the case of compressors that have multiple refrigerant feed devices, that is to say for example in the case of multi-stage compressors, it is preferable for at least sections of all of the refrigerant feed devices for feeding refrigerant to the compression device to be arranged so as to be thermally separate from one, multiple or preferably all of the refrigerant discharge devices that are provided (for example device for discharging refrigerant which is at an intermediate pressure or at high pressure or compression end pressure). In this way, the heat transfer is reduced for all of the refrigerant feed devices, that is to say for example for the feeds to all stages of the compressor.

In a further preferred embodiment, in the case of compressors that have multiple refrigerant feed devices, that is to say for example in the case of multi-stage compressors, at least two or more of the refrigerant feed devices are thermally separate from one another in each case at least over sections thereof. In particular if the refrigerant to be fed to a compression stage is provided for example for cooling a drive device of the compressor, thermal decoupling from the one or more other refrigerant feed devices is often desirable. In general, it can be stated that such a construction should always be considered if the corresponding refrigerant feed devices conduct refrigerant at different temperatures.

In a further preferred embodiment, in the case of compressors that have multiple refrigerant discharge devices, that is to say for example in the case of multi-stage compressors, at least two or more of the refrigerant discharge devices are thermally separate from one another in each case at least over sections thereof. This is advantageous for example if the respective refrigerant discharge devices conduct refrigerant at different temperatures. This situation may conceivably arise for example in the case of a two-stage compressor in which the refrigerant at the outlet of one compression stage may possibly be at a temperature that differs from that at the outlet of the other compression stage(s). A transfer of heat to the relatively cold refrigerant that is discharged from the first compression stage can thus be prevented. This contributes to an increase in efficiency of the system.

In summary, it can be stated that a compressor according to the invention in which at least sections of one or more refrigerant feed device(s) are thermally separate or decoupled from one or more of the one or more refrigerant discharge device(s) provided in the compressor permits an increase in the efficiency of the compressor. By means of optional further (additional) thermal separation between the refrigerant feed devices themselves and with respect to the refrigerant discharge devices and between the refrigerant discharge devices themselves, it is possible in the case of respective compressor constructions, in particular in situations in which temperature differences prevail between the individual devices, to achieve a further improvement in efficiency.

The wording “thermally separate”, as it is used in the present application, will be explained in more detail at this juncture. Within the context of the present application, “thermally separate” means not thermally coupled or relatively weakly thermally coupled, that is to say with the least possible heat transfer. This may be achieved for example by means of a spacing between corresponding components and/or by virtue of said components being formed as separate structural parts. A further alternative is for the individual sections to be separated from one another by means of an insulating material. This may be used even if several of the feed devices and of the discharge devices for refrigerant are to be formed as an integral component. It is conceivable for the entire component to be produced from a material with a low thermal conductivity, preferably lower than the thermal conductivity of C-45 steel, furthermore preferably lower than a thermal conductivity of 20 W/mK, in particular preferably lower than a thermal conductivity of 10 W/mK. Here, even wall thicknesses of a few mm are effective. It would alternatively be conceivable to use two-component constructions, for example with insulating layers, wherein, in this case, the structural parts are again spaced apart from one another by the insulating layer. Possibilities for minimizing the heat transfer are accordingly an elimination of contact areas, a minimization of the existing or required areas, the selection of a low-conductivity material for required areas, in particular contact areas, and the thermal insulation of areas, in particular contact areas, by means of corresponding materials or substances (solid matter insulation, gas insulation, if appropriate insulation by means of liquid) and/or by means of a corresponding spacing to one another.

Even though a compressor according to the invention is explained on the basis of the example of a multi-stage radial piston-type compressor in the following description of the figures, the construction according to the invention can be applied to any desired single-stage and multi-stage compressor, regardless of the compression principle thereof. Aside from radial piston-type compressors, reference is made, by way of example, to axial piston-type compressors, scroll-type compressors, screw-type compressors, turbocompressors, rotary compressors, etc.

Further features of the invention are specified in the subclaims.

The invention will be described below with reference to the appended drawings and on the basis of preferred embodiments. In the drawings:

FIG. 1 shows a first possible embodiment of a compressor according to the invention;

FIG. 2 is a schematic illustration of a refrigeration system which has a compressor according to a first possible embodiment, and an enthalpy-pressure diagram applicable thereto;

FIG. 3 is a schematic illustration of a refrigeration system which has a compressor according to a second possible embodiment according to the invention, and an enthalpy-pressure diagram applicable thereto;

FIG. 4 is a further schematic illustration of a (third) refrigeration system which constitutes a modified refrigeration system in relation to FIG. 2, and an enthalpy-pressure diagram applicable thereto;

FIG. 5 is a schematic illustration of a (fourth) refrigeration system which again constitutes a modified refrigeration system in relation to FIG. 2, and an enthalpy-pressure diagram applicable thereto;

FIG. 6 is a schematic illustration of a (fifth) refrigeration system which again constitutes a modified refrigeration system in relation to FIG. 2, and an enthalpy-pressure diagram applicable thereto;

FIG. 7 shows, in a schematic illustration, a sixth refrigeration system which constitutes a modification of the system as per FIG. 3, and an enthalpy-pressure diagram applicable thereto;

FIG. 8 shows a view of a power unit of the compressor as per the first embodiment, in section perpendicular to the axial direction; and

FIG. 9 shows a further sectional illustration of the compressor as per FIG. 8, in a section parallel to the axial direction.

The first embodiment, illustrated in FIG. 1, of a compressor according to the invention is a radial piston-type compressor 10 which has a drive device or a drive unit in the form of an electric motor 12 and a compression device or compression unit 14. Both the electric motor and also the compression unit 14 are arranged in a compressor housing 15 which is assembled from two parts, specifically a motor housing 15-1 and a pressure cover 15-2. The motor housing 15-1 is connected to the pressure cover 15-2 in gas-tight fashion. Said compressor is accordingly a compressor of hermetic type of construction, or a hermetic compressor for short. In the present embodiment, the two housing parts are welded to one another, wherein other thermal connecting methods, for example brazing etc., or other suitable gas-tight connecting methods, such as flanging, adhesive bonding etc., are also conceivable.

In the embodiment described here, the compression unit has six pistons 18 extending away from a central axis 16 in a radial direction, which pistons are arranged so as to be displaceable back and forth in a radial direction in corresponding cylinders or cylinder bores 19. The compression unit 14 is driven by means of a drive shaft 16 which is connected rotationally conjointly to the electric motor 12 and which is in operative engagement with the pistons 18 via an eccentric mechanism and connecting rods. In alternative embodiments, any number of pistons other than six is also conceivable. The number of pistons is specified on the basis of the desired specifications and the desired field of use. The functioning of the compression process itself is well known both for the radial piston-type compressor described here and also for all other possible compressor types, and will not be described in any more detail at this juncture.

The compressor 10 is a two-stage compressor, the compression unit 14 of which is designed to compress refrigerant in two stages. For this purpose, refrigerant for a first compression stage 14-1 is supplied to the compressor 10 by means of a low-pressure refrigerant feed device 20 which delimits a low-pressure volume of the compressor 10 (suction volume), said refrigerant being compressed in said first compression stage to a predetermined intermediate pressure. It is pointed out at this juncture that the compressor according to the invention may alternatively self-evidently also be in the form of a single-stage compressor or any other compressor type (scroll-type compressor etc., of single-stage or multi-stage design). In the embodiment described, use is made of a reciprocating-piston compressor, because this can be used advantageously inter alia owing to its high sealing action arising from the use of cylinders (good sealing by means of the piston rings). Furthermore, it is also the case that the regions around the cylinders, that is to say for example regions that are, in part, subject to intense loading, are subject to thermal loading (as a result of the heating caused by the compression of the refrigerant) only at the moment of compression, that is to say when the cylinder is charged with refrigerant and the piston approaches top dead center. Cooling subsequently takes place immediately for example by means of an inflowing refrigerant, such that the material loading is kept as low as possible.

The low-pressure refrigerant feed device 20 has multiple sub-regions. These are a first low-pressure refrigerant feed device sub-region 20-1, which is formed and defined by a tubular wall or by a pipe and which extends outside the compressor housing 15 from the compressor housing 15 to a low-pressure port 22, a second low-pressure refrigerant feed device sub-region 20-2 which is again formed and defined by a tubular wall or by a pipe and which extends within the compressor housing 15 from the compressor housing 15 to the compression unit 14, and a third low-pressure refrigerant feed device sub-region 20-3, which is formed in the compression unit 14. In the described embodiment, the sub-regions are each formed by separate components which, at the ends, are each connected in gas-tight fashion to a corresponding end of one of the other components. It is pointed out at this juncture that the entire low-pressure refrigerant feed device 20 may alternatively be formed in one piece, or may have a number of components that deviates from three. The extent of the sub-regions mentioned above need not correspond to the extent of the components.

After being fed to the first compression stage 14-1, which is formed by four of the six cylinders, the refrigerant is compressed, in the first compression stage, to an intermediate pressure. After being compressed by the first compression stage 14-1, the refrigerant is discharged into an intermediate pressure refrigerant discharge device 24, which in turn has three sub-regions: a first intermediate pressure refrigerant discharge device sub-region 24-1 which is again delimited by a tubular wall of by a pipe and which extends outside the compressor housing 15 from the compressor housing 15 to a first intermediate pressure port 26; a second intermediate pressure refrigerant discharge device sub-region 24-2 which is likewise delimited by a tubular wall or by a pipe and which extends within the compressor housing 15 from the compressor housing 15 to the compression unit 14, and a third intermediate pressure refrigerant discharge device sub-region 24-3, which is formed in the compression unit 14 and which serves for connecting the second intermediate pressure refrigerant discharge device sub-region 24-2 to the cylinders, more precisely to the outlets of the cylinders of the first compression stage 14-1. The intermediate pressure refrigerant discharge device sub-regions are in turn, analogously to the low-pressure sub-regions, connected in gas-tight fashion at respective ends to one another and at corresponding other ends to the first intermediate pressure port 26 and to the cylinders of the first compression stage 14-1. The statements made with regard to the low-pressure feed device 20 also apply analogously with regard to the number of components.

By means of the intermediate pressure refrigerant discharge device 24, the refrigerant that is at intermediate pressure is conducted out of the compressor and made available, at the first intermediate pressure port 26, for transfer to an intermediate cooler 28 (in this regard, cf. FIG. 2). In an exemplary refrigeration system which is illustrated in FIG. 2 and which has a compressor 10 as per FIG. 1, the compressor 10 is, by way of the first intermediate pressure port 26, connected via a first pipeline 30 to the intermediate cooler in which the refrigerant that is at intermediate pressure is cooled. Via a further, second pipeline 32, the cooled refrigerant that is at intermediate pressure is then transferred via a second intermediate pressure port 34, which is connected to the second pipeline 32, into an intermediate pressure refrigerant feed device 36 of the compressor 10.

In the embodiment described, the intermediate pressure refrigerant feed device 36 has two sub-regions that are connected to one another in gas-tight fashion: a first intermediate pressure refrigerant feed device sub-region 36-1 which again is of tubular form and which is arranged between the compressor housing 15 and the second intermediate pressure port 34 and is connected in gas-tight fashion to the latter, and a second intermediate pressure refrigerant feed device sub-region 36-2 which is of tubular form and which extends from the compressor housing 15 toward the electric motor 12 by way of a 90° bend and which ends in the region of the electric motor 12. In this way, in the possible embodiment that is described, the cooled refrigerant that is at intermediate pressure is used for cooling of the electric motor 12. By means of a third intermediate pressure refrigerant feed device sub-region 36-3 which is arranged in the compression unit 14, the cooled refrigerant that is at intermediate pressure is then fed, after flowing through and cooling the motor, to a second compression stage 14-2 which is composed of two cylinders and in which said refrigerant is compressed to a high pressure (high pressure). For this purpose, the cylinders of the second compression stage 14-2 are connected in gas-tight fashion at an inlet side to the third intermediate pressure refrigerant feed device sub-region 36-3. The intermediate pressure refrigerant feed device 36 may also be composed of any desired number of components, which need not correlate with the corresponding sub-regions.

After being compressed to high pressure, the refrigerant is then discharged from the cylinders (outlets) of the second compression stage 14-2 into a high-pressure refrigerant discharge device 38. The high-pressure refrigerant discharge device 38 has five high-pressure refrigerant discharge device sub-regions which are each connected to one another in gas-tight fashion: a first, tubular high-pressure refrigerant discharge device sub-region 38-1 which extends outside the compressor housing 15 from the compressor housing 15 to a high-pressure port 40; a second high-pressure refrigerant discharge device sub-regions 38-2 which is likewise of tubular form and which extends within the compressor housing 15 from the compressor housing 15 to a third high-pressure refrigerant discharge device sub-region 38-3; the third high-pressure refrigerant discharge device sub-region 38-3 which is of approximately cuboidal form, that is to say has a rectangular cross section, and which serves for pulsation damping in the high-pressure volume 38; a fourth high-pressure refrigerant discharge device sub-region 38-4 which extends from the third high-pressure refrigerant discharge device sub-region 38-3 to the compression unit 14; and a fifth high-pressure refrigerant discharge device sub-region 38-5 which is formed in the compression unit 14 and which is connected to cylinder outlets of the second compression stage 14-2 and which serves for the discharge of refrigerant at high pressure or compression end pressure. Again, use may be made of any desired number of components, and the number of sub-regions does not need to correlate with the number of components, and the boundaries between sub-regions do not need to correspond to boundaries between components, as is also the case for the other feed and discharge devices.

In the exemplary refrigeration system of FIG. 2, the refrigerant is fed from the high-pressure port 40 via a third pipeline 42 to a gas cooler 43 in which said refrigerant is cooled. The cooled refrigerant that is at high pressure subsequently flows via a fourth pipeline 44 into a first expansion element 46, where said refrigerant is expanded to a medium pressure, which does not need to correspond to the intermediate pressure. Via a fifth pipeline 48, the refrigerant then flows into an accumulator 50, from which said refrigerant passes via a sixth pipeline 52 into a second expansion element 54, in which it is expanded to low pressure (intake pressure), and subsequently via a seventh pipeline 56 to an evaporator 58. From the evaporator 58, the refrigerant then flows via a further, eighth pipeline 60 to the compressor 10, more precisely to the low-pressure port 22 of the compressor 10.

For the compression of refrigerant, and in particular for the compression of natural refrigerant, such as for example CO2 which is used as refrigerant in the embodiment described here, it is important that the (gaseous) refrigerant is not unnecessarily heated before it enters the respective compression stage. Since the admissible compression end temperature is restricted, any heating before the actual compression entails a restriction of the achievable compression ratio and an increase in the expenditure of work per unit of mass of compressed refrigerant.

It is therefore provided that a section of each refrigerant feed device 20, 36 is arranged so as to be thermally separate from the refrigerant discharge devices. This relates, in the present embodiment, to sections which begin at respective ports for the refrigerant (low-pressure port 22, second intermediate pressure port 34), and in the case of the low-pressure refrigerant feed device, said section comprises the first low-pressure refrigerant feed device sub-region 20-1 and the second low-pressure refrigerant feed device sub-region 20-2. In the case of the intermediate pressure refrigerant feed device 36, said section comprises the first and the second intermediate pressure refrigerant feed device sub-region 36-1 and 36-2.

Furthermore, the intermediate pressure refrigerant discharge device 24 and the high-pressure refrigerant discharge device 38 are also thermally separate from one another. In the case of the intermediate pressure refrigerant discharge device 24, the corresponding section comprises the first and the second intermediate pressure refrigerant discharge device sub-regions 24-1 and 24-2, and in the case of the high-pressure refrigerant discharge device 38, the corresponding section comprises the first to fourth high-pressure refrigerant discharge device sub-regions 38-1 to 38-4.

The respective sections that are arranged so as to be thermally separate from one another are arranged spaced apart from one another and are thermally separate or decoupled from one another by the respective ambient atmosphere (in the compressor, by refrigerant which is either at intermediate pressure or at intake pressure, and outside the compressor, by ambient atmosphere).

Furthermore, FIG. 2 illustrates a corresponding pressure-enthalpy diagram for the refrigeration system, wherein the states denoted by single-digit numerals in the pressure-enthalpy diagram arise at the locations in the system denoted by circled single-digit numerals. The states in the respective pressure-enthalpy diagrams of FIGS. 3 to 7 are denoted analogously. This will therefore not be pointed out individually again, wherein it should rather be assumed to have already been explained that the respective pressure-enthalpy diagrams illustrated in FIGS. 3 to 7 represent the states in the refrigeration systems illustrated in each case in the same figure. The states denoted by a numeral prevail in each case at that location of the refrigeration system which is denoted by a circled numeral.

FIG. 3 illustrates a further exemplary refrigeration system which has a second possible embodiment of a compressor according to the invention. The compressor 110 is again of two-stage design, and corresponds substantially to the compressor 10 of the first described embodiment as per FIG. 1. At this juncture, a description will be given in particular of the differences with respect to the compressor 10 as per FIG. 1. The compressor 110 has two compression stages 114-1 and 114-2.

By contrast to the first possible embodiment, the first compression stage 114-1 compresses a coolant main flow which is at low pressure (intake pressure), which is provided to the compressor 110 via a low-pressure port 122 and a low-pressure volume, which corresponds in terms of construction and function to that of the first embodiment, to high pressure. Arranged parallel to said first compression stage is the second compression stage 114-2 by means of which refrigerant of a coolant secondary flow, which is at intermediate pressure, is likewise compressed to high pressure. The refrigerant that is at intermediate pressure is fed to the compressor 110 via an intermediate pressure port 134, which corresponds to the second intermediate pressure port 34 of the first embodiment, and via an intermediate pressure volume which is connected to said intermediate pressure port and which corresponds in terms of design and function to the second and immediate pressure volume of the first embodiment. Here, too, the refrigerant that is at intermediate pressure is used for the cooling of the electric motor of the compressor.

By contrast to the compressor 10 of the first embodiment, it is the case in the compressor 110 that the cylinders (cylinder outlets) of the two compression stages 114-1 and 114-2 are connected to a common high-pressure sub-volume 138-5, which replaces the fifth high-pressure sub-volume 38-5 of the first embodiment, which is connected only to the cylinders (cylinder outlets) of the second compression stage 14-2. The remaining sub-volumes of the high-pressure volume of the second embodiment, too, are of analogous design to those of the first embodiment; a high-pressure port 140 which corresponds to the first embodiment is also provided.

Therefore, in the case of the compressor 110 of the second embodiment, the first intermediate pressure volume 24, via which, in the first embodiment, the refrigerant that is compressed in the first compression stage 14-1 of the compressor is fed to the intermediate cooler, is eliminated without replacement.

From the high-pressure port 140, the refrigerant flows (again in each case via pipelines) to a gas cooler 143, which corresponds in terms of design and functionality to the gas cooler 43, and is cooled there. The refrigerant flow is subsequently divided into the main flow H and the secondary flow N, wherein the secondary flow passes through a first expansion element 146-1 where it is expanded to the intermediate pressure of the compressor. The secondary flow N is subsequently fed to a heat exchanger 162. The main flow H does not flow initially through an expansion element and is instead fed directly to the heat exchanger 162, such that the main flow H is cooled further by the secondary flow N.

The secondary flow is then conducted to the second compression stage 114-2, more precisely to the intermediate pressure port 134, whereas the main flow H passes through an expansion element 146-2 which expands the refrigerant of the main flow, or the main flow, to a medium pressure which may differ from the intermediate pressure. After passing through an accumulator 150, which corresponds in terms of design and function to the accumulator 50 of the first embodiment, and a further expansion element 154, which corresponds in terms of design and function to the expansion element 54 of the first embodiment, the refrigerant of the main flow H then passes back to the low-pressure port of the compressor 110 via the evaporator 158.

It is pointed out at this juncture that, in both of the described embodiments of a compressor according to the invention, the rotor of the electric motor 12 functions as an oil separator. In the embodiments described, the compressor housing 15 is composed of two parts which, after the insertion of the drive device and the compression unit, are thermally connected to one another in non-disassemblable fashion. This leads to a high level of durability of the compressor, because loosening of connections, for example owing to vibrations, is unlikely. It is alternatively also possible for the housing 15 to be formed from more than two parts, which may, despite a greater number of parts and slightly higher production costs, increase ease of assembly and thus provide cost savings elsewhere.

A third refrigeration system which is based on the compressor 10 and which is a modification of the refrigeration system illustrated in FIG. 2 is illustrated in FIG. 4. In addition to the components provided in FIG. 2, the third refrigeration system has a connecting line in the form of a pipeline 64 between the accumulator 50 and the pipeline 32, which connecting line is arranged between the intermediate cooler 28 and the second intermediate pressure port 34. A secondary flow of refrigerant from the accumulator 50 to the second compression stage 14-2 is thus made possible.

A further (fourth) refrigeration system which is based on the compressor 10 is illustrated in FIG. 5. In this embodiment, the intermediate cooler 28 together with the pipelines associated therewith are dispensed with; the fourth refrigeration system is however otherwise identical to the third refrigeration system as per FIG. 4.

A fifth refrigeration system illustrated in FIG. 6 is again based on the refrigeration system of FIG. 2 (two-stage compressor with compression stages arranged in series), wherein it is however the case that the refrigerant flow is divided, downstream of the gas cooler 43 (analogously to the situation in the refrigeration system illustrated in FIG. 3) into a main flow H and a secondary flow N, wherein the secondary flow passes through a first expansion element 46-1, where it is expanded to the intermediate pressure of the compressor. The secondary flow N is subsequently fed to a heat exchanger 62. The main flow H does not initially pass through an expansion element, and is instead fed directly to the heat exchanger 62, such that the main flow H is cooled further by the secondary flow N.

The secondary flow is then fed to the second compression stage 14-2, more precisely to the intermediate pressure port 34, whereas the main flow H passes through an internal heat exchanger 66 and then an expansion element 54, the refrigerant of the main flow H then passes back to the low-pressure port of the compressor 10 via the evaporator 58, a further accumulator 68 and the internal heat exchanger 66.

FIG. 7 finally again shows a further (sixth) refrigeration system which has a compressor 110 (that is to say a compressor with parallel compression stages 114-1 and 114-2). By contrast to the refrigeration system as per FIG. 3, the sixth refrigeration system however does not have a heat exchanger that transmits heat from a refrigerant main flow to a refrigerant secondary flow. Similarly to the situation in the refrigeration system of FIG. 5, the entire refrigerant flow passes through an expansion element 146 and subsequently passes into a separator or accumulator 150. From the accumulator 150, a connection in the form of a pipeline 164 extends to the inlet of the compression stage 114-2, whereby a secondary flow N is fed to the compression stage 114-2, whereas a main flow H is fed to the expansion element 154 and, via the evaporator 58 arranged downstream thereof, to the first compression stage 114-1.

As already indicated above, the described first embodiment of a compressor 10 constitutes a compressor 10 with an eccentric mechanism. The corresponding power unit will be discussed in more detail below, said discussion however being based on a compressor according to the invention which does not by any means need to be a reciprocating-piston compressor but which may also be a scroll-type compressor, a screw-type compressor or any other known design of compressor. The power unit described below however constitutes an advantageous variant in particular for situations in which it is the intention or imperative for radial piston compressors to be used owing to technical prerequisites or else owing to customer demands and the like.

As emerges from FIGS. 8 and 9, the compressor 10 (which may also be used as the compressor 110) has six pistons 18 which are arranged so as to be movable back and forth in a radial direction in corresponding cylinder bores or cylinder liners 216. The cylinder bores or cylinder liners 216 themselves are formed as corresponding cutouts in a cylinder block 218. The pistons 18 are, as already mentioned above, designed to be movable back and forth in the radial direction. With regard to said back and forth movement, a distinction will hereinafter be made between deployment movement and retraction movement, wherein the deployment movement takes place in the radially outwardly oriented direction (indicated by arrow 220) and the retraction movement takes place in a radially inwardly oriented direction (indicated by arrow 222). As already mentioned above, the compressor 10 serves for compressing R744 (CO₂) as refrigerant. It is however pointed out that the use of any other desired refrigerant (for example R134a, etc.) is also conceivable.

Furthermore, the compressor 10 has the drive device in the form of the drive shaft 16 (in this regard, cf. for example FIG. 9) by means of which the compressor 10 is driven. In the embodiment described, the drive shaft is coupled to the electric motor 12, though in alternative embodiments may also be coupled to a corresponding belt drive device or to some other device. It is pointed out at this juncture that the axial extent of the drive shaft 16 may also be considerably shorter, depending on the intended use, than in the embodiment illustrated in the figures, in which the drive shaft 24 is in operative engagement with, and extends through, the electric motor.

During the course of the deployment and retraction movements of the pistons, during a retraction movement of the pistons 18, refrigerant is drawn into the cylinder bores or cylinder liners 216, and during the deployment movement, said refrigerant is compressed and then discharged.

The drive device in the form of the drive shaft 16 is in operative engagement with an eccentric 228. More precisely, the drive shaft 16 is of eccentric design in a corresponding region (eccentric section of the drive shaft 16). The eccentric 228 is thus formed on the drive shaft 16 so as to be integral and in one piece therewith. In alternative embodiments, the eccentric 228 may also be formed as a separate component and fastened to, in particular articulatedly connected to or correspondingly mounted on, the drive shaft 16.

In a section perpendicular to the axial direction, the eccentric 228 has a circular cross section and radially outwardly directed eccentric surfaces 230, which are arranged in a region of an eccentric action section 232. The eccentric action section 232 serves for driving the piston 18 and is in operative engagement with the latter in each case via a connecting rod 234 associated with each piston 18. For this purpose, the connecting rods 234 are articulatedly connected to the pistons 18 by way of connecting rod eyes 236 which are formed on those sides of the connecting rods 234 which face toward the pistons 18.

On the side facing toward the eccentric 228, the connecting rods 234 have a connecting rod action section 238 which serves for the operative engagement with the eccentric 228. The eccentric 228 is in operative engagement with the connecting rod action sections 238 via a bearing in the form of a needle-roller bearing 240 which is arranged (fitted) on the eccentric action section 232 (circular cross section), specifically on the eccentric surface 230 thereof. Other bearings, in particular plain bearings or rolling bearings or bearings of any possible design, are conceivable as an alternative to needle-roller bearings 240.

The bearing 240 serves for low-friction transmission and conversion of the movement (rotary movement) of the eccentric 228 into a radially directed movement of a connecting rod action section receptacle 242 which is in operative engagement with the bearing by way of a corresponding fit. The corresponding movement in the radial direction is then correspondingly transmitted to the connecting rods 234 and to the pistons 18 that are articulatedly connected thereto. For this purpose, the connecting rod action sections 238, which are designed correspondingly to the circular outer circumference of the bearing 240 and which are of circular-segment-like form at their side facing toward the bearing 240, have a broadened extent in the axial direction at their end facing toward the bearing, such that said connecting rod action sections are securely arranged on the bearing 240 by way of two shells 244 which are of L-shaped form in cross section and which form the connecting rod action section receptacle 242. The connecting rod action sections of all of the connecting rods 234 are arranged on a circular path around the eccentric 228 and thus also around the eccentric action section 232, which is concentric therewith.

Owing to the fact that the pendulum point of the device is arranged eccentrically owing to the use of the eccentric 228, it is possible in the case of the present design, in which use is made of circular-segment-like connecting rod action sections 238 and in which the connecting rods 234 are thus decoupled from one another in terms of their movement, for different movements to take place in each case in the region of the respective pistons 18. If the connecting rods 18 were rigidly coupled, this would result in a deficiency in the stroke movement and thus in an increased dead space in the region of the pistons 18 situated remote from the pendulum point.

It can be stated that the compressor 10 and also the compressor 110 have inter alia the following design features, in particular in addition to the fact that at least one section of a refrigerant feed device or at least one section of at least one, in particular each refrigerant feed device is arranged so as to be thermally separate from a refrigerant discharge device or at least one, in particular each of multiple refrigerant discharge devices:

-   1. Compressor for compressing refrigerant, having a drive device, in     particular drive shaft, for driving one or more pistons which are     arranged in a radial direction and which are movable back and forth     in deployment and retraction movements in corresponding cylinder     bores, wherein the drive device is in operative engagement with an     eccentric which controls the deployment movement of the pistons,     wherein the eccentric also controls the retraction movement of the     pistons. -   2. Compressor as described under 1., wherein the eccentric has an     eccentric action section by way of which it is in operative     engagement with one or more connecting rods, in particular     connecting rod action sections of the respective connecting rods. -   3. Compressor as described under 2., wherein the compressor has, for     each piston, a respectively associated connecting rod which is     articulatedly connected to said piston by means of a connecting rod     eye, the latter being formed on a side, which faces toward the     respective piston, of the connecting rod. -   4. Compressor as described under 2. or 3., wherein the compressor     has, for each piston, a respectively associated connecting rod which     is operatively connected to the eccentric by means of the connecting     rod action section, the latter being formed on a side, which faces     toward the eccentric action section, of the connecting rod. -   5. Compressor as described under 2., 3. or 4., wherein the eccentric     action section has a circular cross section and/or wherein those     sides of the connecting rod which face toward the eccentric action     section, in particular the connecting rod action section, are of     circular-segment-like form. -   6. Compressor as described under 2., 3., 4., or 5., wherein the     connecting rod action sections are arranged on a circular path     around the eccentric, in particular concentrically around the     eccentric action section. -   7. Compressor as described under 6., wherein a bearing, in     particular a needle-roller bearing, is arranged between the     connecting rod action section and the eccentric action section. -   8. Compressor as described above, wherein the compressor is a     compressor of hermetic type of construction.

Even though the invention has been described on the basis of embodiments with specific combinations of features, the invention however also comprises the conceivable further advantageous combinations that are specified in particular, but not exhaustively, by the subclaims. All of the features disclosed in the application documents are claimed as being essential to the invention where they are novel, individually or in combination, in relation to the prior art.

LIST OF REFERENCE NUMERALS

-   10, 110 Compressor -   12 Electric motor -   14 Compression device -   14-1, 114-1 First compression stage -   14-2, 114-2 Second compression stage -   16 Drive shaft -   18 Piston -   19 Cylinder -   20 Low-pressure refrigerant feed device -   22 Low-pressure port -   24 Intermediate pressure refrigerant discharge device -   26 First intermediate pressure port -   28 Intercooler -   30, 32 Pipeline -   34 Second intermediate pressure port -   36 Intermediate pressure refrigerant feed device -   38 High-pressure refrigerant discharge device -   40, 140 High-pressure port -   42 Pipeline -   43, 143 Gas cooler -   44 Pipeline -   46, 146 Expansion element -   48 Pipeline -   50, 150 Accumulator -   52 Pipeline -   54, 154 Expansion element -   56 Pipeline -   58, 158 Evaporator -   60 Pipeline -   62, 162 Heat exchanger -   64 Pipeline -   66 Internal heat exchanger -   68 Accumulator -   216 Cylinder bores/cylinder liners -   218 Cylinder block -   220 Arrow -   222 Arrow -   228 Eccentric -   230 Eccentric surface -   232 Eccentric action section -   234 Connecting rod -   236 Connecting rod eye -   238 Connecting rod action section -   240 (Needle-roller) bearing -   242 Connecting rod action section receptacle -   244 Shell 

1. A compressor, having a compressor housing, having a drive device and having a compression device with one or more compression stages for compressing a refrigerant, wherein the compressor furthermore has one or more refrigerant feed devices for feeding refrigerant to the compression device and one or more refrigerant discharge devices for discharging refrigerant from the compression device, wherein at least one section of one refrigerant feed device or at least one section of at least one, in particular each of the multiple refrigerant feed devices is arranged so as to be thermally separate from one refrigerant discharge device or at least one, in particular each of the multiple refrigerant discharge devices.
 2. The compressor as claimed in claim 1, wherein the compressor has more than one refrigerant feed device, is in particular of multi-stage design, and at least one section of each refrigerant feed device is arranged so as to be thermally separate from the one or more refrigerant discharge devices.
 3. The compressor as claimed in claim 1, wherein the compressor has more than one refrigerant feed device, is in particular of multi-stage design, and at least one section of each refrigerant feed device is arranged so as to be thermally separate from every other refrigerant feed device that is provided.
 4. The compressor as claimed in claim 1, wherein the compressor has more than one refrigerant discharge device, is in particular of multi-stage design, and at least one section of each refrigerant discharge device is arranged so as to be thermally separate from every other refrigerant discharge device that is provided.
 5. The compressor as claimed in claim 1, wherein the one or more sections that are arranged so as to be thermally separate from the other refrigerant feed device(s) or refrigerant discharge device(s), or separate from sections thereof, are formed separately from these and/or are arranged so as to have no contact surface or a minimized contact surface with respect to one another and/or so as to be spaced apart from these and/or so as to be separated from these by a thermally insulating material or a material that exhibits low thermal conductivity.
 6. The compressor as claimed in claim 1, wherein one or more of the sections that are arranged so as to be thermally separate from other refrigerant feed device(s) or refrigerant discharge device(s) extend from the inner side of the compressor housing to the compression device.
 7. The compressor as claimed in claim 1, wherein one refrigerant feed device opens out in the compressor housing, in particular in the region of or adjacent to the drive device.
 8. The compressor as claimed in claim 7, wherein the refrigerant feed device that opens out in the compressor housing is a refrigerant feed device for refrigerant which is at low pressure or for refrigerant which is at an intermediate pressure.
 9. The compressor as claimed in claim 1, wherein at least one refrigerant discharge device, in particular a refrigerant discharge device for refrigerant which is at an intermediate pressure, is provided for connecting to an inlet of a refrigerant intercooler of a refrigeration system or is in fluid communication with an inlet of a refrigerant intercooler of the compressor.
 10. The compressor as claimed in claim 7, wherein the refrigerant feed device that opens out in the compressor housing is provided for connecting to an outlet of a refrigerant intercooler of a refrigeration system or is in fluid communication with an outlet of a refrigerant intercooler of the compressor.
 11. The compressor as claimed in claim 1, wherein the drive device has an electric motor with a rotor and a stator, wherein the rotor serves as an oil separator for refrigerant that is supplied thereto.
 12. The compressor as claimed in claim 1, wherein the compressor is of two-stage design and has a refrigerant feed device for refrigerant at low pressure and a refrigerant feed device for refrigerant at intermediate pressure and a refrigerant discharge device for refrigerant at intermediate pressure and a refrigerant discharge device for refrigerant at high pressure, wherein in each case at least sections, in particular sections arranged within the compressor, of each refrigerant feed device and of each refrigerant discharge device are arranged so as to be spaced apart from one another.
 13. The compressor as claimed in claim 1, wherein the compressor is provided for R744 as refrigerant.
 14. The compressor as claimed in claim 1, wherein the compressor has at least two housing components which are connected to one another in gas-tight and non-disassemblable fashion, and/or the compressor is of a hermetic or semi-hermetic type of construction.
 15. A refrigeration system, comprising a compressor as claimed in claim
 1. 16. The refrigeration system as claimed in claim 15, comprising an intercooler for cooling refrigerant that is provided by a refrigerant discharge device of the compressor. 